title: Atmospheric pressure chemical ionization Fourier transform ion cyclotron resonance mass spectrometry for complex thiophenic mixture analysis.
abstract: BACKGROUND
  Polycyclic aromatic sulfur heterocycles (PASHs) are detrimental species for refining processes in petroleum industry. Current mass spectrometric methods that determine their composition are often preceded by derivatization and dopant addition approaches. Different ionization methods have different impact on the molecular assignment of complex PASHs. The analysis of such species under atmospheric pressure chemical ionization (APCI) is still considered limited due to uncontrolled ion generation with low- and high-mass PASHs.
  
  
  METHODS
  The ionization behavior of a model mixture of five selected PASH standards was investigated using an APCI source with nitrogen as the reagent gas. A complex thiophenic fraction was separated from a vacuum gas oil (VGO) and injected using the same method. The samples were analyzed using Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS).
  
  
  RESULTS
  PASH model analytes were successfully ionized and mainly [M + H](+) ions were produced. The same ionization pattern was observed for the real thiophenic sample. It was found that S1 class species were the major sulfur-containing species found in the VGO sample. These species indicated the presence of alkylated benzothiophenic (BT), dibenzothiophenic (DBT) and benzonaphthothiophenic (BNT) series that were detected by APCI-FTICR MS.
  
  
  CONCLUSIONS
  This study provides an established APCI-FTICR MS method for the analysis of complex PASHs. PASHs were detected without using any derivatization and without fragmentation. The method can be used for the analysis of S-containing crude oil samples.
authors.affiliation: Clean Combustion Research Center, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Kingdom of Saudi Arabia.
authors.forename: Nadim
authors.initials: N
authors.lastname: Hourani
authors.forename: Jan T
authors.initials: JT
authors.lastname: Andersson
authors.forename: Isabelle
authors.initials: I
authors.lastname: Möller
authors.forename: Ma'an
authors.initials: M
authors.lastname: Amad
authors.forename: Matthias
authors.initials: M
authors.lastname: Witt
authors.forename: S Mani
authors.initials: SM
authors.lastname: Sarathy